As known, certain mushroom varieties, e.g. pleurotus ostreatus (oyster mushroom) can be cultivated on trees, cereals and on various agricultural byproducts. Various methods are known for preparation of the substrate required for cultivation. Each method is aimed at producing favorable conditions in the substrate for the cultivation of the mycelium of the mushroom. In the course of this, the substrate of the mushroom contains nutrients and water. In addition, the preparation seeks to eliminate or substantially reduce the many other competing microorganisms such as mildews, bacteria in the raw material, and to eliminate their conditions of existence. Thus, the mycelium of the mushroom inoculated into such substrate will grow quickly without competition. So the substrate is produced from dry raw materials by wetting, then by elimination of the detrimental effect of the competing microorganisms. After inoculation, the substrate so prepared is interwoven. The interwoven material is used for further inoculation, this inoculum in interwoven condition is used for fodder, or for mushroom cultivation.
Three methods of the most frequently used heat treatment are known for reducing the detrimental microorganisms from following the wetting. The first heat treatment method is aimed at propagation of the thermophile bacteria in the substrate for providing the required protection. In the course of this heat treatment, the wetted raw material is heated to max. 60.degree. C. temperature, incidentally to 70.degree. C., for 2-3 hours, against insect pests, followed by cooling below 60.degree. C., then it is held at 50.degree.-55.degree. C. for 2-3 days under adequate airing. In this case, the thermophile bacteria propagating in very large quantity consume the nutrients mostly of the mildews and other microorganisms, as a result of which a cetain degree of protection is developed in the substrate. According to this method, the wetted raw material is heated by steam, or immersion into hot water or by the socalled mass heat treatment. After cooling to under 30.degree. C., the heat treated substrate can be inoculated with mycelium without special hygienic conditions. Then it is bagged into packing material, is interwoven and is ready for use.
According to the second method of heat treatment, the wetted raw material is heated to 70.degree.-100.degree. C. in the course of the partial sterilization and is held there for 1-6 hours. In this case, the pests in the raw material and the vegetative forms of the competing microorganisms are destroyed, except those present in persistent spore form. Following the holding time, the substrate is quickly cooled below 30.degree. C. and is inoculated with the mycelium of the selected mushroom. Strict hygienic conditions are required for the inoculation, since the partial sterilization does not protect the substrate against the reinfecting organisms arriving from the air, or from other accessories. After inoculation and bagging, strict hygienic conditions have to be maintained for the substrate also during interweaving. Therefore, the packing material should be sealed to insure adequate sterility. The interwoven material protects itself against infections, and thus the cultivation takes place under normal circumstances.
The third kind of heat treatment is the sterile method. Here the wetted raw material is filled and sealed into suitable packing material, then together with the packing material it is heated to and held at 110.degree.-135.degree. C. under autoclave pressure. Under the effect of this temperature, the pests and all microorganisms, that is fungi, spores, and bacteria present in the raw material are destroyed. Then the autoclave together with the substrate is cooled to a predetermined temperature, followed by taking the packing material out of the autoclave and cooling it to under 30.degree. C. Then the packing material is opened and the substratum is inoculated with mycelium under very strict hygienic conditions, then sealed again under sterile conditions. Thereafter the substrate is interwoven and put to use. This method is suitable mainly for the production of inoculum.
For the technical realization, preparation, inoculation and bagging of the sterile substrate, the following methods and accessories that are described below are used.
The comminuted or fine grained raw material e.g. grain of wheat is first wetted or precooked for the purpose of adequate water intake. The wetting is carried out generally manually by sprinkling and mixing, and in case of large quantities with the use of conveyors such as belts, etc. Various intermittent and continuous cooking appliances are used for precooking of the granular raw material. After cooking and drying, the prewetted and cooked material is filled generally by hand into packing material, most frequently into preserving bottles, then sealed manually under sterile conditions. The bottles are placed into autoclaves possibly by the use of a lifting basket, then sterilized under suitable pressure and temperature. After the holding time, the bottles in the autoclave are cooled to a desired temperature, then are removed from the autoclave and allowed to cool naturally to the inoculation temperature. Thereafter the bottles are opened manually under sterile conditions, the substrate is inoculated manually with grain germ or inoculating rod, then the bottles are sealed again by hand. This is followed by interweaving of the substrate at the proper place. Such apparatus and accessories are described e.g. in the book of Szili, I.--Vessey, E. titled: "Household cultivation of champignon and other mushrooms", 1980, p. 185-204.
The nearly sterile heat treatment of the substrate is carried out in smaller quantities also in autoclaves, similarly as before, but at a lower temperature. The inoculation and interweaving are the same as those described for the sterile method. In the case of large quantities, the wetted raw material is filled into boxes or plastic bags in heat insulated steaming premises and is then heated by steam to the required temperature, then held at that temperature, followed by cooling down quickly with air current. The heat treated substrate is carried out of the steaming premises. It is spread out and inoculum is mixed in either by machine or manually, then filled again into boxes or bags. The inoculation may take place in packing material used in the steamer with the insertion of inoculating rod or with inoculation by hand. After inoculation, the bags are sealed by a sterile method. The inoculation takes place in both cases under strict hygienic conditions. Then the substrate is interwoven under increased hygienic conditions.
Drawbacks of the prior art practices are that the processes and apparatus used for preparation, inoculation and bagging of the sterile and nearly sterile substrate are known only separately for each step. Another drawback is that the above manufacturing phases were carried out in separate locations, using different apparatus. Accordingly, these processes required much handling and several manual steps. Further drawbacks of the prior art processes are connected with the sensitivity to infection of the heat treated substrate received from the surroundings, namely that each process, namely transfer and opening entails an increased infection hazard. The autoclave processes have an additional drawback that due to the unfavorable heat transfer conditions only small units, that is maximum 5 liters can be heat treated, and even that with unnecessarily high energy utilization. Cleaning of the bottles before they are used again represents additional cost. Further drawback of the prior art methods is the great deal of manual work, the great deal of material handling required, which all unfavorably influence the cost and the economic efficiency of these prior art methods. These drawbacks are increased in the case of large scale production. For this reason the sterile process is economical in industrial quantities only for the production of mushroom germ. Large scale preparation, inoculation and bagging of substrate for mushroom cultivation could not be developed either with sterile or partially sterile method for want of suitable process and apparatus.